As shown in FIGS. 1 and 2, the conventional filament heater and electric conduction plate is constructed of a seat 12 which is provided with a plurality of holes 13 on the surface and attached to an inner electric conduction plate 14. The surface of the inner electric conduction plate 14 has a plurality of circular holes 15 that correspond to the plurality of holes 13 of the seat 12 and that also hold the filament heater 16. The surface of filament heater 16 is attached to an outer electric conduction plate 17 which also contains mounting holes 18 to match each location of filament heaters 16. The edge of mounting hole 18 is formed with ring trough 19, so as to enable the outer electric conduction plate 17 to use ring trough 19 of mounting hole 18 to connect to the edge surface of filament heater 16 secured by a plurality of screws 20 fastening both outer electric conduction plate 17 and seat 12. Furthermore, the inner electric conduction plate 14 together with the outer electric conduction plate 17 clip the filament heater 16 in place. However, such construction as described above is defective in design for the following reasons:
1. The process in manufacturing the filament heater 16 must be very accurate. If it happens to be rough and uneven in its surface, then the filament heater 16 cannot be tightly mounted between the inner electric conduction plate 14 and outer electric conduction plate 17. Therefore, it is easy to create poor electric conduction or cause a spark in electric current because of the space therebetween. As a result, producing a filament heater 16 with the necessary precise flatness is very difficult and is not cost effective to manufacture. PA0 2. The inner electric conduction plate 14 and outer electric conduction plate 17 must also be very accurate for tightly mounting the filament heater 16. This is especially true for the outer electric conduction plate 17 which is the main member in mounting the filament heater 16. Therefore, the outer electric conduction plate 17 is formed with ring trough 19 for attaching to the edge surface of filament heater 16. If the process in manufacturing the outer electric conduction plate 17 happens to deform the ring trough 19 or if the ring trough 19 is not planar for any reason, then the outer electric conduction plate 17 cannot be tightly mounted to the filament heater 16. It causes the construction of the conventional filament heater and electric conduction plate to poorly conduct electricity in the filament heater 16. In addition, since the surface of filament heater 16 cannot contact closely with the inner electric conduction plate 14 and outer electric conduction plate 17, it is therefore likely to produce a spark from the electric current in the space therebetween and to potentially create a dangerous fire situation.